02/22/2014

Outline

The Qweak Experiment

The First Results

Analysis Update

Publications & Outreach

Summary

Adesh SubediFor the Qweak Collaboration

Hall C Users Meeting

Status Update of the Qweak Analysis

Weak charge of the proton(Qw(p))

o Neutral current analog of electric chargeo The SM has a firm prediction of its value based on the running of the weak mixing angle (sin2 ϴw) from measured Z pole value

o In general, Qw(Z,N) = -2{C1u(2Z+N) + C1d(Z+2N)} o Accidental suppression makes it sensitive to new physicso Measures quark vector coupling combination 2C1u + C1d

2

= -2C1u

= -2C1d

= -2 (2C1u + C1d)

= -2 (C1u + 2C1d)

Determining Qw(p)

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where σ± is ep x-sec for e’s of helicity ±1

This Experiment

Z0

EM (PC) + neutral-weak (PV)

are weak and axial FFs

Experimental Apparatus

Parameters:Ibeam = 180 μAEbeam= 1.160 GeVθ = 6° - 12°Integrated rate = 6.4 GHzBeam Polarization = 88%Target = 34.5 cm LH2

Cryopower = 3 kW

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PVES Asymmetryo Parity transformation is equivalent to helicity reversal

o Pseudo random quartet ordering frequency ~ 1 kHz

o Asymmetry formed by a quartet (4 ms) A =

o Statistical power is ΔA = σquartet/√N = 226 ppm/ √N

where N is the number of quartets

Detector signal integrated in each helicity window

226 ppmper quartet

Blinded asymmetry 5

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Target Designo World’s highest power cryogenic target ~2.2 kW of

beam powero Designed with computational fluid dynamics (CFD) to

reduce density fluctuations

IBeam = 180 uAL = 35 cm (4% X0)Pbeam = 2.2 kWAspot = 4x4 mm2

V = 57 litersT = 20.00 KP ~ 2.2 atm

Centrifugal pump(15 l/s, 7.6 kPa)

3 kW Heater

3 kW HX utilizing4K & 14K He coolant

35 cm cell (beam interaction volume)

Solid Tgts

6/3/2013

Fluid velocity

beam

beam

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Nominal running point

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Target Performance

Time (sec)

Time (sec)

Pump speed = 28.5 Hz

From 3 independent ways, tgt. noise at 960 Hz reversal rate , 180 μA beam <50 ppm

Very small contribution to the total measured quartet asymmetry width (226 ppm)

Pump speed = 12 Hz

Mai

n D

ete

cto

r Y

ield

(V

/μA

)

4x4 mm2 raster 169 μA beam current

o Correction of false asymmetriesAmsr= Araw +Areg + AT + AL

Areg = Linear regression asym.AT = Residual transverse asym.AL = Non-linearity in signal chain

o Normalization with beam polarization (P) and correction for various backgrounds

Rtot = RQ2RRCRDetRBin

fi = fraction of yield from bkgd. i ( Al window, Soft neutral, Beamline, Inelastic)Ftot = ∑ fi = 3.6 % Ai = Asymmetry of bkgd. i

𝑨𝒆𝒑 = 𝑅𝑡𝑜𝑡

𝑨𝒎𝒔𝒓

𝑷− Σi=1

4 𝐟𝐢𝐀𝐢

1− Σ𝐟𝐢

Extracting Physics Asymmetry (Aep)

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Aep = -279 ± 35 (statistics) ± 31 (systematics) ppb

o Global fit of PVES data on H, 4He and D was used to extract QpW - Qweak, G0,

HAPPEX, SAMPLE, PVA4

o Effectively five parameters used in fit:

– C1u and C1d

– strange charge radius (ρs) and magnetic moment (μs)

– isovector axial form-factor GAZ (T=1) A (isoscalar form factor GA

Z (T=0) taken from theory)

o Energy and Q2 dependent electroweak correction from □ ϒz made at kinematics of each proton experiment before fit

o Resulting fit is APV (ϴ,Q2)

o QpW taken as the intercept of fit of APV/A0|ϴ=0 vs Q2

Determination of the Weak Charge of the Proton

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Determination of the Weak Charge of the Proton

o PVES data points shown on this plot have been extrapolated to ϴ= 0 using global fit

o Reduced parity violating asymmetry

Weak charge of the protonQp

W (PVES) = 0.064 ± 0.012Qp

W (SM) = 0.0710 ± 0.0007

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AP

V/A

0

Determination of the Weak Vector Charges of the Quarks

o C1 coefficients of light quarks C1u = -0.1835 ± 0.0054 C1d = 0.3355 ± 0.0050

o Weak charge of the neutron Qn

W (PVES+APV) = -0.975 ± 0.010 Qn

W (SM) = -0.9890 ± 0.0007

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Running of sin2ϴw

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First Resultso Only from 4% of the total data

Aep = -279 ± 35 (statistics) ± 31 (systematics) ppb

o Weak charge of the proton

QpW (PVES) = 0.064 ± 0.012

QpW (SM) = 0.0710 ± 0.0007

o C1 coefficients of light quarks

C1u = -0.1835 ± 0.0054

C1d = 0.3355 ± 0.0050

o Weak charge of neutron

QnW (PVES+APV) = -0.975 ± 0.010

QnW (SM) = -0.9890 ± 0.0007

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Hydrogen datao Replay of data almost done

o Work on various small corrections continues

o Slow helicity reversal by using Insertable Half Wave Plate (IHWP) in the injector

o Null asymmetry formed by averaging asym. ((IN+OUT)/2) without correcting for sign changes due to IHWP

o A null asymmetry is strong evidence that the rapid reversal (with regression) cancels HC false asymmetries

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Note: Partial Run II dataStat. error onlyNo other corrections

Polarization

o Møller Polarimeter

Run II polarization measurements available (~ 0.8% precision)

Run I had a defective quadrupole coil

- POISSON magneto-static field generator used to produce an altered quadrupole field map to be included in Møller simulation

o Compton Polarimeter Settled discrepancy in scaler(untriggered) vs. accumulator (triggered) mode of polarization measurements Comparison with Møller polarization measurements being doneMore systematic studies underway

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Q2 Acceptance Determination

o Improvements on Horizontal Drift Chamber calibrations being implemented

o Time and octant variation of Q2 being investigated

o Simulations being done to understand the data

o Still aiming for 0.5% precision on Q2

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Q2 (GeV/c)2

Q2 comparison : Data (red) and simulation (black)

Al background

o Measured asymmetry is close to the anticipated asymmetry. Null asymmetry ((IN + OUT) /2) is consistent with zero

o Dilution studies underway

o Simulations efforts ongoing to understand contributions due to other elements on the aluminum alloy

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Other Ancillary Measurements

o Parity-conserving transverse asymmetry in elastic e-p scattering at E = 1.165 GeV(See Buddhini’s talk next)

o Inelastic parity-violating asymmetry in the N→Δ transition at E = 0.877 and 1.165 GeV

o Inelastic parity-violating asymmetry at W = 2.5 GeV

o Parity-violating asymmetry in pion photo-production at E = 3.3 GeV

o Parity-conserving transverse asymmetry in elastic e-27Al and e-12C at E = 1.165 GeV

o Parity-conserving transverse asymmetry in the N→Δ transition at E = 0.877 and 1.165 GeV on p, 27Al, 12C

o Parity-conserving transverse asymmetry in Møller scattering at E = 0.877 GeV

o Parity-conserving transverse asymmetry in inelastic scattering near W = 2.5 GeV

o Parity-conserving transverse asymmetry in pion photoproduction at E = 3.3 GeV

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Publications & Outreacho The first results published in PRL 111, 141803 (2013)

o Drafts being prepared for transverse asymmetry measurements in elastic e-p scattering, general Nuclear Instruments and Methods (NIM), target NIM and main detector NIM

o Enthusiastic reception of the results in various conferences like INPC, DNP, DSPIN, LANSPA etc. Plethora of conference proceedings

o 2013 JSA thesis prize & 2014 DNP dissertation award to Katherine Myers

o 2013 Jlab Users’ Group poster competition awards to Buddhini Waidyawansa (1st) and Josh Magee (3rd)

o Many press releases on the Qweak

experiment

http://physicsworld.com/cws/article/news/2013/sep/16/experiment-probes-strength-of-the-weak-interaction

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Summary

o Qweak results from 4% data agree with the SM predictions

o Least noise achieved from the highest power cryogenic target ever used in a parity

violating experiment

o Full analysis ongoing. Expect 5x more statistical precision on the asymmetry than

the published result

o Data look good. No smoking guns found yet

o Systematics likely to be constrained close to their proposed values

o Theory community at work to refine gamma-z box contribution

o Constraints on new physics in terms of mass limits being investigated

o Many publications to come

o And a lot of dissertations – including mine!!

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The Qweak Collaboration

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D. Androic,1 D.S. Armstrong,2 A. Asaturyan,3 T. Averett,2 J. Balewski,4 J. Beaufait,5 R.S. Beminiwattha,6 J. Benesch,5

F. Benmokhtar,7 J. Birchall,8 R.D. Carlini,5, 2 G.D. Cates,9 J.C. Cornejo,2 S. Covrig,5 M.M. Dalton,9 C.A. Davis,10 W. Deconinck,2

J. Diefenbach,11 J.F. Dowd,2 J.A. Dunne,12 D. Dutta,12 W.S. Duvall,13 M. Elaasar,14 W.R. Falk,8 J.M. Finn,2, T. Forest,15, 16 D. Gaskell,5

M.T.W. Gericke,8 J. Grames,5 V.M. Gray,2 K. Grimm,16, 2 F. Guo,4 J.R. Hoskins,2 K. Johnston,16 D. Jones,9 M. Jones,5 R. Jones,17

M. Kargiantoulakis,9 P.M. King,6 E. Korkmaz,18 S. Kowalski,4 J. Leacock,13 J. Leckey,2, A.R. Lee,13 J.H. Lee,6, 2, L. Lee,10

S. MacEwan,8 D. Mack,5 J.A. Magee,2 R. Mahurin,8 J. Mammei,13, J.W. Martin,19 M.J. McHugh,20 D. Meekins,5 J. Mei,5 R. Michaels,5

A. Micherdzinska,20 A. Mkrtchyan,3 H. Mkrtchyan,3 N. Morgan,13 K.E. Myers,20 A. Narayan,12 L.Z. Ndukum,12 V. Nelyubin,9

Nuruzzaman,11, 12 W.T.H van Oers,10, 8 A.K. Opper,20 S.A. Page,8 J. Pan,8 K.D. Paschke,9 S.K. Phillips,21 M.L. Pitt,13 M. Poelker,5

J.F. Rajotte,4 W.D. Ramsay,10, 8 J. Roche,6 B. Sawatzky,5 T. Seva,1 M.H. Shabestari,12 R. Silwal,9 N. Simicevic,16 G.R. Smith,5

P. Solvignon,5 D.T. Spayde,22 A. Subedi,12 R. Subedi,20 R. Suleiman,5 V. Tadevosyan,3 W.A. Tobias,9 V. Tvaskis,19, 8

B. Waidyawansa,6 P. Wang,8 S.P. Wells,16S.A. Wood,5 S. Yang,2 R.D. Young,23 and S. Zhamkochyan 3

Spokespersons Project Manager Grad Students

97 collaborators 23 grad students

10 post docs 23 institutions

Institutions:1 University of Zagreb2 College of William and Mary3 A. I. Alikhanyan National Science Laboratory 4 Massachusetts Institute of Technology5 Thomas Jefferson National Accelerator

Facility6 Ohio University7 Christopher Newport University8 University of Manitoba,9 University of Virginia10 TRIUMF11 Hampton University12 Mississippi State University13 Virginia Polytechnic Institute & State Univ14 Southern University at New Orleans15 Idaho State University16 Louisiana Tech University17 University of Connecticut18 University of Northern British Columbia 19 University of Winnipeg20 George Washington University21 University of New Hampshire22 Hendrix College, Conway23 University of Adelaide

Thank You !

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Backup Slides

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Beam parameters

Beam Parameter@ the tgt.

Modulation Amplitude

Required Δχi

(entire expt.)Required

Δχi

(monthly)

Msrd ∂A/∂χi

(monthly)

X ± 125 μm < 2 nm 4.1 nm -1.67 ppm/μm

X’ ± 5 μrad < 30 nrad 0.16 nrad 83 ppm/μrad

Y ± 125 μm < 2 nm -6.4 nm 0.27 ppm/μm

Y’ ± 5 μrad < 30 nrad 0.34 nrad -3.6 ppm/μrad

Energy ± 61 ppm~ 70 keV

< 3.5 nm 13.7 nm -1.53 ppm/μm

Charge asymmetry

- < 0.1 ppm 0.14 ppm -

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